qemu/fpu
Peter Maydell 3c85c37f25 softfloat: Fix factor 2 error for scalbn on denormal inputs
If the input to float*_scalbn() is denormal then it represents
a number 0.[mantissabits] * 2^(1-exponentbias) (and the actual
exponent field is all zeroes). This means that when we convert
it to our unpacked encoding the unpacked exponent must be one
greater than for a normal number, which represents
1.[mantissabits] * 2^(e-exponentbias) for an exponent field e.

This meant we were giving answers too small by a factor of 2 for
all denormal inputs.

Note that the float-to-int routines also have this behaviour
of not adjusting the exponent for denormals; however there it is
harmless because denormals will all convert to integer zero anyway.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Richard Henderson <rth@twiddle.net>
2014-01-08 19:07:22 +00:00
..
softfloat-macros.h softfloat: Fix shift128Right for shift counts 64..127 2013-06-10 11:36:12 -05:00
softfloat-specialize.h softfloat: implement fused multiply-add NaN propagation for MIPS 2012-10-31 22:20:45 +01:00
softfloat.c softfloat: Fix factor 2 error for scalbn on denormal inputs 2014-01-08 19:07:22 +00:00